I just had my car in the shop. They replaced the coolant tank that has the sensor on it. After testing, they said that the replacement was bad. Then they replaced it again and now my coolant light keeps coming on.

Ah my mistake, missed the location. Well if cooling system is functioning properly, perhaps there is some sort of a short on the sensor lead. Sorry I can't be of more help. Still getting used to how nearly every aspect of these cars is computer controlled. Another trip to the dealer perhaps? Best of luck!

Not entirely sure on bmw's, but on my s2000 the same lead would be reused and just the sensor at the end replaced. Looking at the previous generation 3 series it is similar, so I imagine the F30 would be as well. However, I have seen that a few people with F30's have had faulty coolant sensors, which were of course replaced by the dealer. That's the only thing that pops into my head regarding the light coming on

By the way a question like this, I live in montreal canada which is pretty cold. Do someone experience this but it takes about 10mins for the car heat to get hot? Sorry i was driving a volvo before and it became hot pretty quick. My 328i seems to take time though but might be normal ???